by clicking the arrows at the side of the page, or by using the toolbar.
by clicking anywhere on the page.
by dragging the page around when zoomed in.
by clicking anywhere on the page when zoomed in.
web sites or send emails by clicking on hyperlinks.
Email this page to a friend
Search this issue
Index - jump to page or section
Archive - view past issues
FLEXO Magazine : June 2012
60-DEGREE HEX The 60-degree hex (Figure 1 and 2) is the standard for qual- ity graphic printing, line type, solids and coatings. This cell configuration has been standard since its original implementa- tion. When the 60-degree hex was first applied, flexo printers experienced approximately 15 percent better ink transfer. This, in turn, allowed for higher engraving specifications cells per inch, or CPI (line screens). The cell cavity and opening is broader than the previous 45 degree standard, allowing for higher CPI and a much better ink transfer rate. Recent laser upgrades have created a slightly broader cell cavity, which has permitted even higher volumes within an engraving specifica- tion. Therefore, higher volumes and higher CPIs have been achieved by approximately 50 percent of users, since that of the original 60-degree engravings of the early 1990s. This geometry has a consistent reaction to most inks and coatings used in the flexo industry. Water-based, solvent and UV inks react about the same when ink formulas and viscosities are correct. With a 60-degree engraving, higher volumes are being achieved up in the range of 70 billion cubic microns (bcm). The 60-degree geometry can be used for many types of coating and printing applications as well. But, the volume needed may affect dryer requirements. When using narrow web press equipment, it is important to make sure the dryer package can handle the pounds per ream of ink or coating being deposited. Running this, or any geometry, can limit how much volume a specific press can manage. This geometry is used for all flexo graphic applications, including coatings and laminations up to 40 bcm. If the chem- istry of the ink or coating is not compatible with this closed cell design, then it would be prudent to switch to one of the alternate geometries to be discussed here. There are also a couple variations of the hex cell that allow it to expand, which may afford better transfer when testing viscous and tacky coatings. This is especially true for blister packaging and other adhesives, like cold seal and hot melt adhesives. It may be necessary to consider an alternative geometry when using this type of specialty application. 70-DEGREE HEX The 70-degree geometry (Figure 3 and 4) is slightly more elongated than the 60 degree. This geometry is fairly new to the industry and has not had enough time in the field to show its real worth. But, in preliminary testing with inks or coatings, 70-degree geometry has shown promise for heavy coating ap- plications. Side-by-side testing has shown that, when process printing through the tonal ranges, the numbers coincide with that of the 60-degree anilox. See Figures 4 and 5 for another example of how this geometry compares to the 60-degree cell. KANTRON –ELONGATED HEX Another new geometry is the elongated hex cell. This cell is similar to the 60-degree cell except extremely elongated. This extension creates thinner walls that may affect overall wear (Figure 5 and 6). Only a few engravers offer this geometry. Cell volumes can be slightly different, depending on where the roller was engraved. All preliminary tests show that the Katron hex can hold and maintain a process graphic. Tests show that there were acceptable similarities throughout the tonal range. But, the question remains: was there any improvement from the 60-de- gree hex? After comparing the results, the graphic reproduc- tion of this Katron did not exhibit enough improvement to warrant a complete inventory change. Further testing is required to determine if the Katron could be used as a coating roller. The volume rating in this cell is approximately double that of a standard 60-degree cell. A banded roller may prove useful to discover any applications that would benefit using a specialty roller. FiGuRE 2 FiGuRE 3 FiGuRE 4 FiGuRE 5 FiGuRE 6 www.flexography.org june 2012 FLEXO 71